Triple positive- 33 years old, will I be given Tamoxifen?

Hi, I have been diagnosed with stage 2 IDC, I am triple positive with no lymph node involvement!  I am 33.  I had a double masectomy on January 14 with immediate reconstruction.  While recovering from surgery I am doing my research on Chemo and the hormonal drugs that may be suggested.  I have been told to expect chemo and herceptin.  Tamoxifen was also suggested but I have read that it's only FDA approved for women over 35.  I am also wondering what kind of research has been done on long term use of this drug, I am assuming I would need to take it longer considering my age.  I may be misunderstanding the use of this drug??

This is my second breast cancer diagnosis, in 2003 I had a malignant phyllodes tumor removed by a lumpectomy.  The pathology of the breast tissue from my masectomy shows a benign phyllodes tumor close to the same area.  I am wondering how this may change my treatment, if at all.